The present invention relates to an apparatus for launching at high velocity an airborne device particularly an aircraft, though any other device could be so propelled.
Aircraft launchers on today's aircraft carriers generally propel the aircraft to be launched using steam that is generated by the same system that provides steam for propulsion of the vessel. Such use of the steam available on seaborne vessels produces a significant weight increase. In the first place, the steam generating machinery must be larger. Secondly, the piping, valves, accumulators and other machinery needed to store steam at high pressure in readiness for application to a catapult launch add weight. Also the conventional steam catapult requires the apparatus for steam launching to be positioned relatively high on the ship. This reduces in a large measure the desirable upper level space required for other purposes. Also the added weight produces a higher center of gravity. Neither of these is a desirable feature in any vessel.
Another drawback of the steam catapult is that it forces, from an overall life-cycle cost standpoint, the use of steam for propulsion rather than such alternatives as gas turbines and diesel engines. Still another drawback is that existing steam catapults are open loop systems: Once the steam launching valve is opened, no further control of the system is provided.
Accordingly, it is desired to provide an internal combustion catapult launcher that is independent of the propulsion plant in that there is no requirement for propulsion steam. Further, it is desired that the launcher have a very accurate end speed control and an acceleration profile that reduces stress on the launcher and aircraft. The internal combustion catapult should be a closed-loop control system in contrast to the conventional steam catapult that is open-loop control. Ideally the system is easily retrofitted to existing steam catapult launchers. It is also desirable that the launch system sense transient conditions such as loss of power from the launching aircraft due to engine failure and compensate by increasing launch force to assure the desired launch end speed. These and many other requirements cannot be met with a conventional steam launching system utilizing the steam from the ship's propulsion system.